Bulletin of the American Physical Society
17th Annual Meeting of the APS Northwest Section
Volume 61, Number 7
Thursday–Saturday, May 12–14, 2016; Penticton, British Columbia, Canada
Session B3: Particle Physics I |
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Chair: Gordon Watts, University of Washington Room: PC 204 |
Friday, May 13, 2016 1:30PM - 2:00PM |
B3.00001: Towards 3000 fb$^{-1}$: ATLAS and CMS detector upgrades Invited Speaker: Wojciech Fedorko Over the next several years the LHC will undertake a two phase upgrade programme culminating in the High-Luminosity LHC upgrade planned to be commissioned in the second half of the next decade. During the first phase the instantaneous luminosity will be raised to 2x10$^{34}$~cm$^{-2}$~s$^{-1}$ and to 5-7x10$^{34}$~cm$^{-2}$~s$^{-1}$ during the second phase, enabling collection of 250~fb$^{-1}$ per year. Such massive datasets are needed to conduct precision measurements of the Higgs boson properties, precision measurements of the Standard Model parameters as well as searches for rare Standard Model processes and Beyond Standard Model physics. The CMS and ATLAS detectors will have to cope with up to 150 interactions per beam crossing and high radiation doses. This necessitates far reaching upgrades to both detectors encompassing tracking, calorimetry and muon detectors as well as front-end electronics and trigger and data acquisition systems. In this talk I will give an overview of the planned Phase I and II upgrades of the ATLAS and CMS detectors. [Preview Abstract] |
Friday, May 13, 2016 2:00PM - 2:15PM |
B3.00002: Using tracking in dense environments to investigate designs for a new ATLAS Inner Detector Felix Cormier Designing the next generation of charged particle trackers for ATLAS under the High-Luminosity LHC regime has the dual challenge of having to operate efficiently at both unprecedented energy - 14 TeV center of mass energy; and at tremendous collision rate - a bunch crossing every 25ns with an estimated 200 pp collisions each bunch crossing. Higher collision energy leads to heavy particles being produced; these then decay into lower mass, high momentum particles that are very close together. Being able to correctly reconstruct these grouped particles, through tracking algorithms like TIDE (Tracking In Dense Environments), is essential for the ATLAS experiment as they are important signatures to many searches. \\ This characterization is implemented starting with a full ATLAS simulation using a baseline geometry; then an algorithm based on track extrapolation is used to cluster each energy deposit independently of the initial geometry, allowing the study of a variety of ATLAS layouts and detector element sizes. Simulated three-prong $\tau$ decays as well as high mass Z$'$ decays - causing collimated particle showers due to hadronization of a quark - are studied to identify the track reconstruction efficiency of different detector geometries to be used in design recommendations. [Preview Abstract] |
Friday, May 13, 2016 2:15PM - 2:30PM |
B3.00003: Searching for `Bumps' in the Dilepton Invariant Mass Spectrum using \textsc{BumpHunter} in $pp$ collision at $\sqrt s = 13$ TeV with the ATLAS Detector Elham E Khoda Additional massive $Z^{\prime}$ gauge bosons occur frequently in the extension of the Standard Model or its minimal supersymmetric extension. The discovery potential of this hypothetical spin$-1$ gauge boson is very high in the run-II of LHC and there is a high possibility of observing dilepton resonance in $2016$ data. The ATLAS experiment searches for proton-proton collisions where two high energy, same-flavour leptons are produced and analyses their invariant mass spectrum. The search incorporates several sophisticated tests to determine the significance of an observed excess. \\ \textsc{BumpHunter} is a model independent statistical test which searches for deviations in the data from the expected background. We study the sensitivity of \textsc{BumpHunter} for discovery in the $2016$ data set. In addition we study several methods, within the \textsc{BumpHunter} framework, for combining data from two channels ($ee, \mu\mu$) of different resolutions. [Preview Abstract] |
Friday, May 13, 2016 2:30PM - 2:45PM |
B3.00004: Searching for High Mass Resonances Decaying to Lepton Pairs using Proton-Proton Collisions at $\lowercase{\sqrt{s}} = 13$ TeV with the ATLAS Detector at the LHC Sebastien Rettie The Standard Model of particle physics is a very successful theory, but it is incomplete as it does not explain neutrino masses or dark matter. Essentially, the Standard Model cannot be extrapolated to the high energy regime of the Planck scale, i.e., the scale at which quantum effects of gravity become strong, in a straightforward manner. To solve these shortcomings, many different extensions to the Standard Model have been posited. Extensions include compositeness models, extra dimensional models, and grand unified theories, which all aim to reconcile the very different scales of electroweak symmetry breaking and the gravitational Planck scale. These theories all predict the existence of new high mass resonances.\\ This analysis is conducted for both resonant and non-resonant new phenomena in dilepton final states. The LHC 2015 proton-proton collision dataset recorded by the ATLAS detector is used, corresponding to 3.2 fb$^{-1}$ at $\sqrt{s}=13$ TeV. The dilepton invariant mass spectrum is the discriminating variable used in this search. No significant deviations from the Standard Model expectation are observed. Lower limits are set on the signal parameters of interest at 95\% credibility level, using a Bayesian interpretation. [Preview Abstract] |
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